Estimating Highway Capacity Considering Two-Regime Models

Capacity can be derived by fitting a relationship between the three fundamental traffic variables: flow, speed, and density. The study uses a dual-regime model with the consideration of all three variables. Different forms of functions were specified for congested and uncongested conditions. An optimization based estimation procedure was developed to minimize the distance between the theoretical functions and the traffic stream variable measurements. The optimal procedure was coded into a computer program and applied to three data sets representing different roadway classifications. The results indicate that the proposed method can produce good estimates of the key traffic stream parameters including the roadway capacity.